The use of lasers in optical data processing systems such as facsimile devices, digital printers and the like have been disclosed in the prior art. A single laser which provides light of single wavelength may be generally utilized for scanning information on a document, the reflected radiation flux being electrically transferred to a storage device or utilized to reproduce the information as a copy of the original document. A scanning laser is generally utilized to reproduce the document information (or for printing puroses only). Typically, a helium-neon laser which generates red laser light when energized has been utilized in many scanning/reproducing applications. For example, Xerox Corporation, Stamford, Connecticut, recently introduced a facsimile device, the Xerox Telecopier 200 (Xerox .RTM. and Telecopier .RTM. are registered trademarks of Xerox corporation) transceiver, which records on plain paper. The transceiver employs a low-energy helium-neon laser and uses the xerographic principle to receive and print messages on ordinary, unsensitized paper. Basically, when the transceiver is in the transmit mode, the laser provides a small stable beam of light to raster scan the original document. The reflected light is detected by a photosensor which translates the white and black of the document to electrical logic levels which may be transmitted by a phone line to a remote transceiver set to the receive mode. The receiver transceiver directs the laser beam onto a xerographic drum and by electrically modulating the laser with "1" and "0" logic levels in synchronism with the transmitter produces a copy of the original.
However, it would be desirable if a single laser could be provided to produce simultaneous laser radiation of more than one wavelength to allow the accurate reproductions of documents which contain information in other than black and white form i.e. multicolored documents.
Although lasers have been produced in the prior art which are capable of producing multiline emissions simultaneously, such as a argon laser, these lasers are generally expensive and large in size, making them inpractical for use in commercial systems, such as the Telecopier 200 transceiver described hereinabove.
An article in the Proceedings of the IEEE, He-Ne-Cd Laser With Two Color Output, S. A. Ahmed et al, Nov. 1969, pages 2084-2085, describes, inter alia, a helium-neon-cadmium laser which produces simultaneous lasing at 4416A and 6328A. However, the laser discharge essentially occurs through a single discharge tube and separate control of the blue (4416A) and red (6328A) laser light is not provided making accurate adjustment of each individual color extremely difficult.
Therefore, a simplified and relatively inexpensive laser which can produce multiline emissions simultaneously, which can be independently controlled and which can be adapted for commercial utilization would satisfy an apparent need in optical data processing technology.